This invention relates to semiconductor memory devices and methods of manufacture, and more particularly to a programmable read only memory (PROM).
Nonvolatile memory devices of the PROM type at the present time usually are bipolar fusable link elements such as shown in U.S. Pat. No. 4,209,894, assigned to Texas Instruments. This technique requires about 30 mA at 15 v to blow out the metal alloy link which provides the memory element. The access time of these devices is degraded because of the physically large transistors necessary to handle the programming power on the chip. Also, reliability problems can result from partial programming due to failure of the decoding circuitry on the chip to deliver the needed power.
It is the principal object of this invention to provide an improved programmable memory. Another object is to provide a PROM of reduced cell size which uses less power for programming. An additional object is to provide a dense array of PROM cells, made by a more efficient method. A further object is to provide a higher speed PROM.